GATE 2020 CY – Question 19

Inorganic Chemistry · Main Group Elements: Shapes and structures of molecules using VSEPR postulates, Hydrides, halides, oxides, oxoacids, nitrides, sulfides - shapes and reactivity. Structure and bonding of boranes, carboranes, silicones, silicates, boron nitride, borazine and phosphazenes: electron counting in polyhedral boranes, isolobal analogy. Allotropes of carbon, phosphorus and sulfur. Industrial synthesis of compounds of main group elements such as NH3, H2SO4 and HNO3. Chemistry of noble gases and interhalogen compounds. Acid-base concepts and principles (Lewis, Brønsted, HSAB and acid-base catalysis). · 1 mark · Multiple choice

Which statement about hexagonal boron nitride is CORRECT?

It is a good electrical conductor.
Its layer stacking is the same as graphite.
It reacts with fluorine.
It is less thermally stable in air than graphite.

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Correct answer: (C) It reacts with fluorine.

Explanation

Hexagonal BN is a wide-band-gap electrical insulator, and its usual stacking differs from graphite’s. Its oxidation resistance in air is high. It can nevertheless be attacked by fluorine, making C the correct listed statement. Chemical inertness toward many reagents does not imply inertness toward all strongly fluorinating conditions.

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All Main Group Elements: Shapes and structures of molecules using VSEPR postulates, Hydrides, halides, oxides, oxoacids, nitrides, sulfides - shapes and reactivity. Structure and bonding of boranes, carboranes, silicones, silicates, boron nitride, borazine and phosphazenes: electron counting in polyhedral boranes, isolobal analogy. Allotropes of carbon, phosphorus and sulfur. Industrial synthesis of compounds of main group elements such as NH3, H2SO4 and HNO3. Chemistry of noble gases and interhalogen compounds. Acid-base concepts and principles (Lewis, Brønsted, HSAB and acid-base catalysis). questions →